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The position of the meridian has changed a few times throughout history, mainly due to the transit observatory being built next door to the previous one (to maintain the service to shipping). Such changes had no significant effect. Historically, the accuracy of the determination of longitude was much larger than the change in position. The adoption of WGS84 as the positioning system, has moved the meridian 102.5 metres east of its last position (measured at Greenwich). The position of the current meridian is not identified at all in Greenwich but is located using a GPS receiver.

He says

"the accuracy of the determination of longitude was much larger than the change in position."

Its apparent to me that the author intends to compare the endemic error in measurement with the size of the change in position in order to show that the changes in position had little significance.

However the sentence as found doesnt say this. I believe that he uses the word accuracy when he means to use the word error. If I were correct, it should read:

"the error in the determination of longitude was much larger than the change in position."

It may have been a translation issue. — Preceding unsigned comment added by 58.160.134.33 (talk) 04:17, 29 December 2014 (UTC)

During my visit to Greenwich on the 3rd of May 2008 I took my GPS navigator (MIO 268, SW 3.2) and hoped to see the coordinate being exactly zero for longitude. I was surprised to see around 0.00147 degrees West, which I roughly calculated into approximately 150m (!) offset. The navigator had a good satellite reception and indicated a 1.6m accuracy. Also the altitude had quite an offset compared to the plaque on the observatory, but I did not make a note of that unfortunately.

How is it possible that the navigator has this enourmous offset and how is it possible that it works fine on the road, on which I believe it is closer to the 1.6m offset than the 150m offset. Does anyone have the same or other experiences? (Marc van Beek, The Netherlands) —Preceding unsigned comment added by 193.173.39.45 (talk) 09:42, 5 May 2008 (UTC)

Marc, your GPS navigator was not at fault. Traditional, or historic, longitude and latitude differ from the longitude and latitude used by GPS systems (see the IERS Reference Meridian section of the Prime Meridian article for an explanation why). --Blake the bookbinder (talk) 05:59, 26 July 2008 (UTC)

No your GPS was not at fault. The adoption of WGS84 moved the meridian east of its current location. This does not appear to be documented anywhere in the Greenwich observatory complex (but I'm wiling to be proven wrong). 109.156.49.202 (talk) 14:45, 29 October 2011 (UTC)

All of these seem to be in accordance with Wikipedia guidelines on capitalisation MOS:CAPS, WP:TITLE, WP:CAPS. This is a matter of house style so the usage in sources in not very relevant: they will be following there own style. SpinningSpark 08:00, 17 April 2012 (UTC)

They had one style and were changed. Some by pointing to dubious Ngrams, then latter other by pointing to books from 1914, while at least one Ngram shows that over time upper case is favored. If less emphasis is put on sources as you say and I agree with, then please, can you tell what is the basis for the moves? Where can one deduct from, that Greenwich Meridian in violating Wikipedia guidelines while Greenwich meridian not? HTML2011 (talk) 17:52, 17 April 2012 (UTC)

I linked you the relevant guidelines above. Did you not look? Extract:

Convention: For page titles, always use lowercase after the first word, and do not capitalize second and subsequent words, unless the title is a proper noun. For multiword page titles, one should leave the second and subsequent words in lowercase unless the title phrase is a proper noun that would always occur capitalized, even in the middle of a sentence.

I did look, but this section is not relevant if one wants to know why the titles were changed to lower case. It says "unless the title is a proper noun". Salt Lake Meridian is a proper noun, so should be capitalized. This is analogous to Rocky Mountains which are not named Rocky mountains in Wikipedia. Also the articles are named South Pole, Southern Hemisphere, New York City, Liard River, Brooks Range and not South pole, Southern hemisphere, New York city, Liard river, Brooks range. The massive renaming by one user brought the meridians out of line with Wikipedia house style. HTML2011 (talk) 21:12, 18 April 2012 (UTC)

BTW, nothing dubious about the page moves. The pages moves definitely occurred. You may disagree with the reasons for the moves, but please refrain from casting the actions of editors your disagree with as "dubious" and assume good faith instead. -- JHunterJ (talk) 21:36, 18 April 2012 (UTC)

Dubious page moves is meant as short for dubious reasons for page moves. Of course I assume the users in questions did it in good faith. HTML2011 (talk) 21:58, 18 April 2012 (UTC)

The reasons are also not dubious, but stated explicitly. -- JHunterJ (talk) 22:00, 18 April 2012 (UTC)

Dubious#Philosophy - it looks dubious to me whether the reasons are valid. "Questionable page moves" might be less objectionable to you? Anyway, could you add an anchor below the section heading, I would like to rename it to "Meridian naming" or so without breaking links, but I don't know how to add anchors. HTML2011 (talk) 22:08, 18 April 2012 (UTC)

I don't think your examples are exactly helping your case. "North Pole" and "New York City" are always capitalised. "Salt Lake Meridian" on the other hand, is not always capitalised. Counter-examples are easy to find: on the first page of gbooks results 8 out of 10 do not capitalise "meridian". SpinningSpark 00:51, 19 April 2012 (UTC)

Your link is great, it shows that the lower casing is almost restricted to pre-1900 literature. We are now in 2012. Also I trust logic more, than gbook digging. Around 1900 there are also many occurrences of "New Yor city". HTML2011 (talk) 01:57, 19 April 2012 (UTC)

Hmm...I am much less confident now that you have pointed out the split by date. The ngram shows that uncapitalised "meridian" was in the ascendency as late as 1974; this does seem to be very much a case of fluctuating styles. But style variation is the very thing the MOS is meant to smooth out. We are supposed to follow the MOS for house style even when the majority of outside publications would do otherwise. On the question of logic, I would say there is a logical difference. "New York City" is a proper noun because it is the generally recognised name of the settlement. "Salt Lake Meridian" is different, it is a meridian at Salt Lake so "Salt Lake meridian" makes equal sense. This is different from "South Pole", a pole at (the) South does not really make sense. One would have to say "a pole at the South Pole" which is unhelpfully redundant. Still, let's here from Dicklyon who executed the moves but, so far, has not taken part here. SpinningSpark 08:46, 19 April 2012 (UTC)

Well that's succesfully broken up the conversation. We should be trying to centralise this discussion. Not spread it all over the wiki. A simple link on pages interested in the central discussion would suffice. So let's say that this discussion is now closed and moved to the MOS page. SpinningSpark 17:35, 19 April 2012 (UTC) and 17:45, 19 April 2012 (UTC)

"The magnetic meridian is an equivalent imaginary line connecting the magnetic south and north poles and can be taken as the horizontal component of magnetic force lines along the surface of the earth.[1][dubious – discuss] Therefore a compass needle will be parallel to the magnetic meridian."

If the magnetic meridian is a component of the magnetic force line (i.e.they are not prallel), and a compass needle alignes with the magnetic force line, then the needle will not be parallel to the magnetic meridian. The one exeption to this is where the magnetic force line is horizontal, which only happens at the equator.

So even if the first section is left unchanged the second section of the quote cannot be correct. I suggest removing the second sentence. — Preceding unsigned comment added by Kabivose (talk • contribs) 20:51, 14 February 2015 (UTC)